Over the past several years there has been increasing concern over the safety of our food supply. Contamination of food can come from a variety of sources and the type of contamination possible is often dependent on the food involved.
Most animal-derived food products, such as raw meat, are exposed to the possibility of contamination before, during, or after processing. Such contamination comes from, for example, contact with fecal matter at the slaughter house, from handlers of the food products at any stage of the processing of the food products, and from toxins, both naturally occurring and man-made, present in the environment where the food was grown or processed. In most cases, contamination is minor and, if the food is prepared properly, is not a serious threat to the consumer. However, while the contamination of food is generally low, i.e., few bacteria per gram of the food, if the food is not stored under satisfactory conditions or stored for long periods of time, contaminants, such as bacteria, grow to become a serious threat to the eventual consumer of the products. Even if the food products reach the market in an acceptable condition, subsequent treatment by the consumer may lead to the development of serious contamination of the food.
A common form of unsatisfactory storage condition involves inadequate temperature management throughout the cold chain. The cold chain is the course of distributing perishable foods from the supplier to the retailer to the consumer. In other words, the cold chain involves the refrigerated transport of food from the processor to the wholesaler, and all of the subsequent steps of storage, handling, and redistribution. Inadequate temperature management or temperature abuse of the food occurs when food is stored at temperatures above the optimal storage temperature and may occur at any point in the food distribution process.
Such time-temperature abuse of the food often results in considerable microbial growth and toxin production by microorganisms introduced through the diverse sources of contamination. Food-borne pathogens like bacteria flourish and increase to hazardous levels if the food is exposed to time-temperature abuse. The presence of bacteria in the food causes the production of off-odors and volatile gases, such as carbon dioxide, sulfur dioxide, hydrogen gas, and organic acids and nitrites in the food. Furthermore, certain kinds of bacteria, such as lactic acid bacteria, cause a decrease in the pH of the food, thus, enhancing further bacterial growth. Other bacteria produce various toxins often implicated in food-borne illnesses. The presence of off-odors, volatile gases, lowered pH, and toxins in the food are thus indicative of bacterial contamination of the food. These contamination-indicating conditions are often referred to as bacterial metabolites as they are the products and by-products of bacterial metabolism.
A number of incidents and factors have lead to the growing concern over food supply. These include:
raw chicken and egg products have been found to be contaminated with Salmonella and inadequate cooking of such products has led to serious illness or death of persons who have consumed the contaminated products; PA1 inadequately pasteurized milk products have been found to be contaminated with Listeria that has lead to serious illness or death of consumers of the products; PA1 a highly toxic strain of E. coli has lead to the death of several people who consumed prepared beef products that had been inadequately cooked; PA1 a number of toxins are known, such as ciguatoxins, which contaminate fish. These toxins are not inactivated or destroyed by cooking and so their presence in fish is a threat to any consumer of the product; PA1 shell fish, such as oysters, concentrate any contaminants present in the water in which they grow and, since they are frequently eaten raw, pose a threat to the health of consumers; and PA1 fish is increasingly eaten raw which adds to the possibility of increased outbreak of illness from water-borne contaminants.
The only means the consumer has of determining if the food they purchase is contaminated is by visual inspection and by smell. These methods are usually inadequate to detect contamination.
There is a need for a reliable way to detect if a food product purchased by a consumer is fit for consumption. Any solution to this problem should be relatively inexpensive and able to detect a number of agents capable of causing illness. It should also be simple to "read" so that a consumer, who does not have access to sophisticated testing equipment or specialized knowledge, can readily determine if the products they have purchased are free from contamination.